Ignition system



May 30, 1967 F. MiERAS ETAL IGNITION SYSTEM 6 Sheets-Sheet 1 Filed April 14, 1965 FIGJ.

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WELL REQ'D.FOR I002. COIL CURRENT I2 56 2O 24 28 32 36 4Q 44 ENGINE SPEED (R.P.M x100) LAURENCE F. Ml ERAS N M m K m s K N A R F BY W M a) 5f. 1) ATTORNEYS y 1967 F. MIERAS ETAL 3,322,107

IGNITION SYSTEM Filed April 14, 1965 v 6 Sheets-Sheet :3

6 I ,2s CONSTANT 'DWELL Z 5 1 uJ D 4 v A z g 3 2 6 2 DWE L REQUIRED-TO ACHEIVE i W 1007. CURRENT sumo P z y o 4 8 l2 I620242832364044 ENGINE SPEED (R.P.M.xl00) F'IG.3 1

DISTRIBUTOR OUTPUT AT H1 H s E I ME IUM I L s E T AN 5? O A L ER-54 '3 E L. o

O 5 50 I5 4O DISTRIBUTOR ROTATION (DEGREES) F'IG.4

' ENTORJ LAURENCE kMlERAS FRANK SKAY A T TORNEY y 1967 L. F. MIERAS ETAL 3,322,107

IGNITION SYSTEM Filed April 14, 1965 6 Sheets-Sheet 5 2? LAURENCE F. MEERAS Q FRANK SKAY mus/v 7095 N (T; q filuwlllllHln- N N g 5: W K). a we WM a ATTORN s May 30, 1967 Filed April 14, 1965 L. F. MIERAS ETAL IGNITION SYSTEM FIG-.62

s sheets-sheet 4 LAURENCE F. MIERAS FRANK" SKAY INVENTORJ A r TORNEVS May 30, 1967 L. F. MIERAS ETAL IGNITION SYSTEM Filed April 14, 1965 FIG '7 6 Sheets-Sheet i) LAURENCE F. MlERAS FRANK SKA? INVENTORY ieywwu 6 ,2

AT TORNEV May 30, 1957 L. F. MIERAS ETAL 3,322,107

IGN TION SYSTEM Filed April 14. 1965 6 Sheets-Sheet LAURENCE. FMEERAS a3: FRANK SKAY INVENTORS United States Patent 3,322,107 IGNITION SYSTEM Laurence F. Mieras, Livonia, and Frank Siray, Detroit, Mich, assignors to Ford Motor Company, Dearborn, Mich, a corporation of Delaware Filed Apr. 14, 1965, Ser. No. 448,061 14 Claims. (Cl. 123148) ABSTRACT OF THE DISCLOSURE An ignition system for an internal combustion engine wherein the secondary winding of an ignition coil is connected sequentially to a plurality of spark plugs by a distributor. The distributor includes an electrical generator having both an engine driven rotor and a stator with an output winding thereon. A source of electrical energy is coupled to the primary winding of the ignition coil through the output winding of the stator. The winding of the stator, in association with a transistor circuit, acts as a switch by completing the circuit from the source of electricity to the primary winding only when the electrical generator generates a voltage above a predetermined magnitude. The electrical generator generates a voltage above the predetermined magnitude at an increased rate in response to an increased speed of the engine. Thus, the primary winding of the ignition coil is coupled to the source of electrical energy for an increasing period in terms of mechanical degrees of rotation of the engine as the speed of the engine increases.

This invention relates to an ignition system for an internal combusion engine, and more particularly to an ignition system for an internal combusion engine in which the dwell varies as a function of engine speed from low engine speeds up to a predetermined speed and thereafter is constant at speeds higher than this predetermined speed.

In conventional ignition systems for internal combustion engines including recently marketed transistorized systems, the dwell, or the period in terms of mechanical degrees of rotation of the engine that the ignition system is energized from the vehicle battery, is substantially constant regardless of the speed of the engine. The dwell must be set or determined in these systems at the high speed range of the engine in order to energize the primary winding sutiiciently at these speeds to produce proper ignition voltage. At low engine speeds, therefore, the primary winding of the ignition coil is energized for a longer period of time than is necessary resulting in a waste of electrical energy.

The present invention provides an ignition system for an internal combustion engine in which the dwell or period in terms of mechanical degrees of rotation of the engine increases significantly from idle speed to a predeter-mined speed in the middle range of the engine. Thereafter it becomes substantially constant. At low engine speeds and up to the predetermined engine speed, the dwell is such that the ignition system is energized just sufiiciently to permit the requisite amount of electrical energy to be stored therein. As a result, the average current is substantially reduced over conventional ignition systems in which the dwell is substantially constant. Above this predetermined speed, the dwell is substantially constant at a value which is normally employed in ignition systems thereby providing sufiicient electrical energy for the system to permit sufiiciently high ignition voltages to be generated.

Preferably, the invention is embodied in a transistorized ignition system that employs a transistor amplifier. In this 3,322,167 Patented May 30, 1967 system, a main switching transistor is coupled to the primary winding of an ignition coil for controlling current therethrough. This transistor is ordinarily biased under steady state conditions to a nonconducting state by means of an amplifier including a transistor that is normally in a conducting state. An electromechanical generator is coupled to this second transistor and when it overcomes the conducting bias or voltage on the second transistor, this transistor will be switched to a nonconducting state and the transistor coupled to the primary winding of the ignition coil will be switched to a conducting state thereby permitting the battery of the vehicle to energize the primary winding of the ignition coil. When the voltage output from the electromechanical generator falls to a level below the bias voltage of the second transistor, this transistor again conducts, the first or main transistor coupled to the primary winding of the ignition coil is switched to its nonconducting state whereby interrupting current in the primary winding of the ignition coil and generating high ignition voltages in the secondary winding of the ignition coil.

The above described ignition system is fully disclosed in a copending application Ser. No. 403,264, filed Oct. 12, 1964 in the name of Frank Skay and assigned to the assignee of this invention, now US. Patent 3,299,875, issued J an. 24, 1967. In that ignition system, the dwell or period of energization of the primary winding of the ignition coil in terms of mechanical degrees of rotation of the engine is substantially constant regardless of engine speed.

In the present invention, the dwell increases as a function of engine speed from idle up to a predetermined speed in the middle speed range of the engine. This is accomplished by means of an electromechanical generator that produces a waveform in which the voltage that is in opposition to the bias on the amplifying or second transistor previously mentioned increases with very small slope or rise time initially and then during the latter portion of the voltage rise rapidly changes to a waveform having a steep slope and a fast rise time. As a result, at low operating speeds when the electromechanical generator is producing a voltage having a small magnitude, the bias on the amplifying transistor will not be overcome until a substantial amount of mechanical rotation of the engine and electromechanical generator have occurred from the zero position of this waveform.

The amplifying or second transistor will be switched to its conducting state and the transistor positioned to control the energy flow through the primary winding of the ignition coil will be switched to its nonconducting state when this waveform again falls below the bias on the amplifying transistor. As a result, during low speed operation the primary winding of the ignition coil is energized for only a short period in terms of mechanical degrees of rotation of the engine and electromechanical generator. As engine speed and the speed of the electromechanical generator increase, the magnitude of the voltage output of the electromechanical generator increases thereby producing the voltage necessary to overcome the biasing voltage on the amplifying transistor earlier in the cycle of the output of the electromechanical generator. This increases the dwell or period of energization of the primary winding of the ignition coil in terms of mechanical degrees of rotation of the electromechanical generator and engine. This increase is a function of engine speed up to a predetermined speed at which the dwell no longer increases substantially as engine speed rises.

The invention thus provides an ignition system in which the primary winding of the ignition coil receives suflicient electrical energy during all engine operating conditions. Simultaneously, this system conserves electrical energy at the lower speed ranges of the engine during which the primary winding of the ignition coil need be energized only for a short period in terms of mechanical degrees of rotation of the engine and electromechanical generator. An object of the present invention is the provision of an ignition system for an internal combustion engine in which the system is energized from a source of electrical energy just long enough during all engine speeds to achieve optimum ignition voltages.

Another object of the invention is the provision of an ignition system for an internal combustion engine in which the amount of electrical energy dissipated by the.

system is just sufficient to provide proper ignition'volt-ages at all engine speeds.

A further object of the invention is the provision of an ignition system for an internal combustion engine that conserves electrical energy but at the same time provides suflicient electrical energy to permit the generation of proper ignition voltages at all engine speeds.

Another object of the invention is the provision of an ignition system in which the dwell, or period that the ignition system is energized in terms of mechanical degrees of rotation of the engine increases with engine speed from engine idle up to a predetermined speed and preferably remains substantially constant at speeds above this speed.

.Other objects and attendant advantages of the present i the dwell is a constant, for example, 28 in an eight cylinder engine, and the dwell in degrees necessary to achieve.

100% current buildup in the ignition coil;

FIGURE 3 is a curve of the input current requirements when the dwell is set at 28, It also shows the input current when'the dwellis just long enough to achieve 100% current buildup;

FIGURE 4 is a curve of the output of the electromechanical generator of the present invention plotted in terms'of mechanical degrees of rotation;

' FIGURE 5 is a schematic diagram of the ignition system of the present invention;

FIGURE 6 is a longitudinal sectional view of the electromechanical generator and distributor of the present invention; 7

FIGURE 7 is a top elevational View partially in section of the electromechanical generator and distributor shown in FIGURE 6;

7 FIGURE 8 is a perspective view of a portion of the stator and rotor of the electromechanical genarator of the invention;

FIGURE 9 is an enlarged sectional'view of the electromechanical generator taken along the lines 99 of FIGURE 6; and f FIGURE 10 is a sectional view partially in elevation of the electromechanical generator taken along the lines 10-10 of FIGURE 9.

Referring'now to the drawings in which like reference numerals designate like parts throughout the several views thereof, FIGURE 1 is a plot of the coil current buildup in percent as a function of time in the primary winding of a conventional ignition coil. It can be seen from this plot that to achieve 100% coil current buildup in the primary winding of a typical ignition coil requires approximately 5 milliseconds. In ignition systems where the dwell (the period that the primary winding is energized in terms of mechanical degrees of rotation of the engine and distributor) the time that the primary winding is energized may be many times that necessary to provide substantially 100% current buildup in the primary winding of the ignition coil at low engine speeds.

Referring now to FIGURE 2, the substantially horizontal curve shows the coil current in terms of maximum coil current for a standard eight cylinder engine at the time that the current through the primary winding is switched or interrupted. The other curve, a straight line at substantially with respect to the horizontal, shows the dwell in degrees of distributor rotation required for coil current as a function of engine speed. It can be seen at low engine speeds, for example, 400 r.p.m.

which is a low idle speed, that the dwell in terms of me-.

chanical degrees of rotation of a distributor that normally has a constant dwell of 28 need only be 5". At 1200 r.p.m. it need be only 17 again considering a distributor which has a normal constant dwell of 28. It can be seen, therefore, that at low engine speeds the dwell period need only be a fraction of that which is necessary at higher engine speeds, and that the dwell required is substantially proportional to the engine speeds up to a certain predetermined speed range.

FIGURE 3 shows average ignition current in amps plotted as a function of engine speed. In FIGURE 3, the substantially horizontal line shows the input current to the ignition coil when the dwell is set at a constant 28 as would be the case in a standard distributor for an eight cylinder engine where-as the straight line positioned at substantially a 45 angle shows the average input current when the dwell is just long enough to achieve 100% current buildup. It can be appreciatedfrom an analysis of these three figures that the ideal situation would be a variable dwell at low engine speeds that increases in substantial proportion to engine speeds with a constant 7 dwell at higher engine speeds. The change from the vari able dwell to the fixed dwell should occur at the engine speed indicated by the intersection of the two curves in FIGURE 3 or, for example, at approximately 2000 r.p.m. engine speed. This type of an arrangement .has the advantage of minimum current consumption at low engine speeds while providing simultaneously at all'engine, speeds suflicient electrical energy to generate the requi site high voltages necessary for proper ignition.

In the invention, an electromechanical generator may be employed to produce an ignition system that hasv a variable dwell that increases as a function of engine speed 7 at the lower speed ranges of the engine. At same prede-f employed. In FIGURE 5 there is shown a circuit diagram of an ignition system that includes'anignition coil 10 having a secondary winding 11. The secondary winding 11 is sequentially connected to spark plugs 12 through a distributor 13. The distributor 13 includes a rotating arm 14 for sequentially'connecting the spark plugs 12 to the secondary winding 11 in synchronismwith the operation of the engine in which the ignition system is mounted.

The primary winding 15 of the ignition coil 10 is energized from the source of electrical energy or storage bat tery 16 under the control of a transistor 17 that is connected in series with the primary winding 15 and the source of electrical energy 16. This is accomplished by connecting the positive terminal 21 of the source of electrical energy 16 to the emitter 22 of transistor 17 by' means of lead 23, lead 24, movable arm 25 of ignition switch 26, contact 27 of this switch, lead 28, ballast resistor 29, lead 30, resistor 31 and lead '32. The collector 33 of the transistor 17 is connected to the primary wind:

ing 15 of ignition coil through lead 34 and resistor 41.

The control of transistor 17 is accomplished by means of a biasing circuit means 42 that includes a second transistor 43 having an emitter 44 connected to the base 45 of transistor 17 through diode 46. The collector 47 of transistor 43 is connected to ground through a base current limiting resistor 49. The emitter 22 and the base 45 of transistor 17 are interconnected through a resistor 51.

The base 52 of transistor 43 is connected to collector 53 of transistor 54 by means of lead 55. The lead 55 and the collector 53 of transistor 54 are connected to ground through a resistor 56. The emitter 57 of transistor 54 is connected to lead 32 through resistor 58.

The base 60 of transistor 54 is connected through lead 61 to one terminal 62 of an annular output winding 63 of an electromechanical generator 64. The other terminal 65 of the output winding 63 is connected to a junction 66 between resistor 67 and the cathode 68 of diode 69. The anode 71 of the diode 69 is connected to junction 72 and this junction in turn is connected to one terminal of resistor 73. The other terminal of the resistor 73 is connected to lead 30. A resistor 74 has one terminal connected to junction 72 and the other terminal connected to junction 75, while a resistor 76 has one terminal connected to junction 75 through lead 77 and the other terminal connected to the base 60 of transistor 54 by means of junction 78. The junction 78 is connected to lead 34 through a feedback resistor 81 and lead 82, and the junction 75 is connected to ground through a lead 83.

The distributor 13 and the electromechanical generator 64 are shown in detail in FIGURES 6 through 10. The distributor 13 and electromechanical generator 64 include a housing 113 that may be suitably mounted in the internal combustion engine by conventional methods or means. The housing 113 is a standard type and may be readily adapted for this use from a standard internal combustion engine distributor. An elongated bearing 114 is positioned within the housing 113 and it rotatably journals a distributor shaft 115. This shaft is also journaled directly within the housing 113 at 116. A gear 117 is fixed to the shaft 115 by means of cross pins 118 and 121. This gear is adapted to be connected to a rotating part of an internal combustion engine so that the shaft 115 is rotated in synchronism with the operation of the engine.

The electromechanical generator 64 includes a stator 122 that has an annular permanent magnet 123 that may be constructed of barium titanite positioned concentrically about the distributor shaft 115. An annular magnetic flux gate element 124 is positioned in radially spaced relationship with respect to the permanent magnet 123.

This magnetic flux gate element is constructed of any suit able ferromagnetic material. The annular output winding 63 is positioned radially outwardly from the magnetic flux gate element 124, and is enclosed in a bobbin 126 constructed of a plastic material that separates or spaces the magnetic flux gate element 124 from the annular output winding 63. The three annular elements, the annular permanent magnet 123, the annular flux gate 124, and the annular output winding 63 including the bobbin 126, are positioned between a lower plate 131 and an upper plate 132 constructed of magnetic material. The two plates 131 and 132 are held between shoulders 134 and 135 of a bushing 136. This bushing is rotatably mounted on the outer diameter of the bearing 114 for limited angular movement about this bearing.

The lower plate 131 has a plurality of upstanding teeth 141 equally spaced about its periphery. The number of teeth 141 corresponds to the number of spark plugs employed in the engine, and as shown in FIGURE 5 and in FIGURE 7,' the distributor 13 and electromechanical generator 64 are designed for an internal combustion engine of eight cylinders that employs eight spark plugs. The upper plate 132 also has a plurality of upstanding shaped teeth 142 that correspond in number to the number of 6 teeth 141 and to the number of cylinders and spark plugs of the engine. As shown in FIGURE 7, the teeth 142 are spaced radially inwardly from the teeth 141 and have one edge in approximate alignment with respect to one edge of the teeth 141.

The rotor 145 of the distributor 13 and the electromechanical generator 64 includes a rotatable plate member or armature 146 that has a number of depending shaped teeth 147 that correspond in number to the number of teeth 141 on the lower plate 131 and to the number of teeth 142 on the upper plate 132.

As can be seen by reference to FIGURES 7 and 9, rotor 145 including rotatable plate member or armature 146 rotates in a counterclockwise direction as viewed in these figures. In FIGURE 9, the trailing edge of each tooth 147 is spaced only slightly from the trailing edge of each tooth 141 at the position shown, while the leading edge of each tooth 147 is spaced only slightly from the leading edge of each tooth 142. Thus, when the rotor 145 is in the position shown on the drawing, the air gap and the flux path that is seen on the right-hand portion of FIGURE 10 that links the annular permanent magnet 123 with the annular output winding 63 is quite small, whereas when the rotor 145 is rotated so that the teeth 147 are positioned intermediate the teeth 141 and 142 as shown in the dotted position, the air gap in this magnetic circuit is very large.

The annular permanent magnet 123 is polarized or magnetized in an axial direction as shown by the arrows in FIGURE 10 so that the flux path will be through the annular permanent magnet 123 and the two plates 131 and 132 that are in contact with the permanent magnet. The annular magnetic flux gate 124 has a small clearance with respect to the upper plate 132 so that a small air gap 148, shown in exaggerated form for the purposes of clarity, exists between these two members. This air gap may be on the order of .050 of an inch, Thus, when the teeth 147 are in the position shown in the dotted line in FIG- URE 9, the reluctance of the flux path through annular flux gate 124, the upper plate 132 and the lower plate 131, is quite small with respect to the parallel path through the lower plate 131, the flange 138, the upstanding teeth 141, the teeth 147 of the armature or plate member 146, and the upstanding teeth 142 of the upper plate 132, and the upper plate 132.

On the other hand, when the teeth 147 are in the solid line position shown in FIGURE 9 and the top side of FIGURE 10, the air gap in the magnetic circuit just previously described through the teeth 141, 142 and 147 may be approximately equal to or smaller than the air gap between the magnetic flux gate 124 and the upper plate 132 thereby providing an alternate path for the flux having a reluctance substantially equal to or less than the reluctance of the path through the annular flux gate 124. Thus, as the shaft is rotated, the flux is alternately shifted from nearly 100% through the annular flux gate 124 to a substantial portion, which may be over 50%, through the parallel path comprising the teeth 141, 142 and 147. Thus, the flux from the annular permanent magnet 123 linking the output winding 63 is alternately increased and decreased thereby generating an alternating output voltage in the annular output winding 63.

These flux paths can be seen by reference to FIGURE 10 where the bottom portion shows the flux path through the annular flux gate 124 when the teeth 147 are in the position shown by the dotted lines in FIGURE 9, and the top portion of this view shows the flux paths when the teeth 147 are in the position shown by the solid lines in FIGURE 9 in which the teeth 147 are in substantial alignment with teeth 141 and 142.

The teeth 141 on the lower plate 131, the teeth 142 on the upper plate 132, and the teeth 147 on the plate 146 of rotor are shaped to produce the voltage waveforms shown in FIGURE 4 in the output winding 63. As shown, the teeth 141 are merely upstanding rectangles formed integrally with the upstanding flange 138 of the plate 131. The teeth 142, on the other hand, are stepped or have a cutout portion 148 when viewed from the top as in sectional views 7 and 9. The teeth 147 are stepped or have a cutout portion 149 when viewed from the side as in the side elevational view of FIGURE 8.

Referring now to FIGURES 4 and 9, the reference for the zero degree line in FIGURE 4 is the intermediate dotted position of the teeth 147 as viewed in FIGURE 9. When the teeth 147 are moving through this position, there is substantially zero flux change in the output winding 63 and thus the output voltage of this Winding is zero.

As the teeth 147 advance in a counterclockwise direction, the leading edges thereof move between the teeth 141 and the cutout portions 148 of the teeth 142, thus gradually increasing the flux through the winding 63 from the magnet 123. This produces the low slope portion of the waveforms just to the right of the zero degree line ororigin as shown in FIGURE 4, When the leading edges of the teeth 147 align themselves with the thicker portions or the ends of the cutout portions 143 of teeth 142, the

i flux linked by the winding 63 increases rapidly thus producing the sharply increased portion of the waveform shown in FIGURE 4. Substantially at this same time, the longer portions of the teeth 147 back of the cut out portions 149 align themselves with the teeth 141 of the lower plate 131 thus adding to the increase in the flux linked by the winding. 7

As the trailing edges of teeth 147 are moved by the trailing edge of the teeth 141, the flux linked by the output winding 63 is decreased rapidly and the high negative voltages, partially shown in FIGURE 4, are generated. r

The distributor 13 and electromechanical generator 64 also include a ceutrifugally actuated advance mechanism that advances the timing of the ignition voltages applied to the spark plugs 12 in accordance with the speed of the 1 engine. Refering to FIGURES 7 and 10, this centrifugally actuated advance mechanism includes a plate 151 rigidly attached to the shaft 115. As shown in FIGURE 3, this f plate 151 has upstanding tangs 153 that extend through apertures 154 in the plate member or armature 146 of rotor 145.,The plate member or armature 146has a pair of upstanding posts 155, and the tangs 153 and the posts [155 are coupled by means of springs 156 and 157. A

post or sleeve 161 is affixed to the armature or plate member 146-and is mounted on shaft 115 for limited angular movement with respect thereto. A pair of centrifugal weights 162 are mounted on upstanding posts 163 that are secured to the plate 151 as shown in FIGURE 7. The plate member or armature 146 has a pair of upstanding flanges 164 and 165 struck therefrom to engage the cam surfaces of the centrifugal weights 162.

Upstanding pillar or post 161 also receivesthe rotor cap 171 that has an electrical contact 172 positioned thereon.

. This electrical contact includes a spring type termination 173 that engages a terminal 174 connected to the lead from the secondary winding 11 of ignition coil 19. This rotor cap 171 is designated in general terms by the numeral 14 and is designated as a rotatable arm 14 in describing the circuit of FIGURE 1. A cap 175 constructed, of insulating material is positioned over the housing 113 and the rotor cap 171. This cap has a plurality of spaced contacts 176 that correspond to the number of spark plugs and cylinders of the engine and that are spaced equally around the perimeter of a circle so that as the rotor cap 171 is rotated by the shaft 115, the secondary winding 11 of ignition coil 19 will be sequentially connected to the spark plugs 12.

i The distributor 13 including the electromechanical generator 64 also includes a standard vacuum advance mechanism 177' as shown in FIGURE 7. This mechanism has an arm 178 connected to the lower plate 131 of stator 122 that includes the annular permanent magnet 123, the annular flux gate 124, the annular output winding 63, and

the upper and lower plates 131 and 132 with spaced teeth 141 and 142. This arm rotates the stator 122 including the bushing 136 about the bearing 114 in accordance with engine vacuum. This changes the position of the teeth 141 and 142 relative to the teeth 147 thereby advancing or retarding the timing of the spark applied to the spark plugs 12 of the internal combustion engine in accordance with engine vacuum.

The output winding 63 is connected to the remainder of the circuit shown in FIGURE 1 'by means of leads, one of which is shown at 179 in FIGURE 6.

In the operation of the electrical generator and distributor, the rotor 145 including the armature or plate 'member 146, the stationary plate 151, the shaft 115, the

pillar 161, and the rotor cap 171, are rotated in a counterclockwise direction when using FIGURES 7 and 9 as a reference. It can readily be appreciated that the teeth 147 of the armature or plate member 146 come into alignment with the teeth 141 and 142 once duringeach eighth of a revolution of the rotor including the shaft 115 and the armature or plate member 146. Thus, 'during'each revolution of the armature or plate member 146' and the shaft 115, eight cycles of alternating electrical energy as shown will be produced inthe'output winding 63. The

eight sets of teeth 141, 142 and 147 when in alignment, act as a parallel magnetic circuit for the flux from the per- 7 manent magnet 123.

As'discussed previously, the centrifugal advance mechanism couples the plate 151 that is aflixed to the shaft 115 i to the armature or plate member 146 and the'post to which the rotor cap 171 is attachedthrough spring mechanisms 156 and 157, the centrifugal weights 162 and up:

standing flanges 164 and 165 of the armature or plate member 146. The higher the speed of the shaft 115 and the plate 151, the greater will be the centrifugal force on the weights 162. This will force the weights outwardly against the flanges 164 and 165, and rotate the armature respect to the rotation of the shaft 115 and the rotationof the engine, thus advancing the timing of the spark as engine speed increases.

It can be appreciated from an inspection of FIGURE 7 that as engine vacuum increases, the stator including the Y permanent magnet-123, the output winding 63 and the upstanding teeth 141 and 142 on the stator structure will of ignition voltages that are applied to the spark plugs, in

accordance with the vacuum present in the engine mani-.

fold.

The alternating voltage output of the output winding 63 as shown in FIGURE 4, is applied to the base 64 of i the transistor 54. This transistor is normally'conducting or, stated differently, is in a conducting state when the circuit is in a steady state conditon.

In normal operation, when the internal combustion en-. gine is running, the movable arm 25 of the ignition switch 26 is in engagement with the ignition contact 27. This connects the source of electrical energy 16 in series with the emitter 22 and collector 33 of transistor 17 and the primary winding 15 of ignition coil 10. At this time, and if it is assumed that the annular output winding 63 is not producing any output voltage, the transistor 54 is biased to a steady state conducting state. This is done by the connection of the emitter 57 of transistor 54 to the positive terminal 21 of the source of electrical energy 16 through the resistor 58 lead 32, and the circuit previously described. The base 60 of this transistor is connected to ground or the negative terminal of the source of electrical energy 16 through resistor 76, lead 77 and lead 83. This provides the proper negative bias on the base 60 with respect to the emitter 57 to bias the transistor 54- into its conducting state. The current flow through the base circuit of this transistor, including the resistor 76 and the circuit previously described, will provide approximately a 0.4 volt negative voltage bias on the base 69 with respect to emitter 57.

With transistor 54 conducting, the transistor 43 will be in a nonconducting state, since the voltage drop across the transistor 54 is so small that the base current of transistor 43, flowing out of base 52, is zero. It can be appreciated that when transistor 43 is in a nonconducting state, transistor 17 will also be in a nonconducting state since no current can flow out of the base 45 of transistor 17 In order to turn transistor 54 oh and to turn transistors 43 and 17 on, it is necessary to overcome the negative bias on the base 60 of transistor 54, and this is done by means of the output voltage from the output winding 63 of the electromechanical generator 64 as shown in FIGURE 4. The bias on the transistor 54 that must be overcome by these voltage Waveforms in order to turn the transistor 54 on, is shown by the dotted line. The voltage waveforms in this figure are designated as low speed, intermediate speed and higher speeds and carry the numerals 181, 182 and 183 respectively.

Referring now to the low speed waveform 181, when the voltage rises to the cross 185 where the waveform 181 intersects the dotted line, the bias on the base 61} of transistor 54 is overcome and the positive potential applied to the base 60 from the output winding 63 blocks current flow from the base thereby turning off transistor 54. This action permits current flow from the base 52 of transistor 43 thereby turning on both transistor 52 and transistor 17.

When the voltage appearing at the terminal 62 drops to the point of the cross 186, the base current from transistor 54 is no longer blocked and, therefore, this transistor will turn on and transistors 43 and 17 will turn off. During the dwell period that transistor 17 is conducting, the period between the two crosses, designated by the numerals 185 and 186, current flows from the source of electrical energy 16 through the emitter 22, collector 33 circuit of the transistor 17, and the primary winding 15 of the ignition coil 10. When the point of the cross 183 is reached, the transistor 54 turns on and transistors 43 and 17 turn off. This interrupts current flow in the primary winding 15 of ignition coil 10, and ignition voltages are generated in the secondary winding 11.

The output voltage of the winding 63 appearing at terminal 62 represented by the voltage waveform 181 then goes negative, and after a time reverses and comes back to the same level that it was at the cross 185. At this time, the transistor 54 will again be turned off and transistors 43 and 17 will be turned on to initiate another ignition cycle.

It can readily be appreciated that the interval between the crosses 185 and 186, between crosses 185' and 186 and between crosses 185" and 186, that is, the period'in terms of distributor or electromechanical generator rotation, that the primary winding of the ignition coil is energized, is the dwell in the ignition system. For the waveform 181 the dwell is 7", for waveform 182 the dwell is 15, and for the waveform 183 the dwell is 28".

It can readily be appreciated from an inspection of FIGURE 4 and from a knowledge of the characteristics of rotating electrical machinery, that as the speed of the engine and electromechanical generator 64 increase (the speed of the shaft 115 and rotor 145 increase) that the magnitude of the voltages generated in the output winding 63 will increase, thereby moving the cross 185 at which the voltage output waveform from the winding 63 crosses the transistor amplifier operating level to the crosses 185' and 185". This increases the dwell substantially as a function of speed. For example, in the intermediate speed rangetypified by the output waveform 182, the dwell is 15 compared to 7 at low speed. At a predetermined speed in the middle speed range of the engine determined by all the parameters involved in the design of the ignition system, the point where the voltage output waveform 183 crosses, the transistor amplifier operating level moves very close to the origin of the waveforms 181, 182 and 183, as shown in FIGURE 4. At that time, the dwell becomes the standard 28. This speed preferably occurs at the intersection of the two curves shown in FIGURE 3, and may be at approximately 2000 rpm. in a standard eight cylinder engine.

As the speed of the engine continues to increase above the predetermined speed described above, it can be seen that the dwell will remain substantially constant since voltage output from the winding 63 of higher magnitude will move the point Where the Waveform 183 crosses the transistor amplifying operating level just a very small amount to the left if any.

The present invention thus provides an ignition system for an internal combustion engine in which the energy dissipated is kept to a minimum While at the same time necessary high ignition voltages are generated. This is done by providing a variable dwell system in which the dwell varies as a function of engine speed from a low speed of the engine to a predetermined speed, preferably in the middle speed ranges of the engine. Thereafter, at speeds above a predetermined speed, the dwell remains constant.

It is to be understood that this invention is not to be limited to the exact construction shown and described, but that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

We claim:

1. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an ignition coil having a primary and a secondary winding, means operated in synchronism with the engine for sequentially coupling said secondary winding of said ignition coil to said spark plugs, a source of electrical energy, and means driven by said engine and operated in synchronism with said first means for periodically coupling said source of electrical energy to said primary Winding of said ignition coil, said means including means for increasing the period that said source of electrical energy is coupled to said primary winding of said ignition coil in terms of mechanical degrees of rotation of the engine as the speed of said engine increases up to a predetermined speed and for maintaining said period sus'btantially constant for all speeds above said predetermined speed.

2. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an ignition coil having a primary and a secondary winding, means operated in synchronism with the engine for sequentially coupling said secondary winding of said ignition coil to said spark plugs, a source of electrical energy, and means driven by said engine and operated in synchronism with said first means for periodically coupling said source of electrical energy to said primary Winding of said ignition coil, said means including means for providing a variable dwell substantially proportional to engine speed from idle speed to a predetermined speed in the middle speed range of the engine and for providing a substantially constant dwell for engine speeds above said predetermined speed.

3. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an ignition coil having a primary and a secondary winding, means operated in synchronism with the engine for sequentially coupling said secondary winding of said ignition coil to said spark plugs, a source of electrical energy, and means driven by said engine and operated in synchronism with said first means for periodically coupling said source of electrical energy to said primary winding of said ignition coil, said means including means for increasing the period that said source of electrical energy is coupled to said primary winding of said ignition coil in terms of mechanical degrees of rotation of the engine as a function of engine speed up to a predetermined engine speed and keeping said period substantially constant for all speeds above said predetermined speed.

4. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an ignition coil having a primary and a secondary winding, a distributor driven by the engine for sequentially coupling said secondary winding of said ignition coil to said spark plugs, a source of electrical energy, said distributor including an electrical generator having a rotor driven by the engine, a stator and an output winding mounted on said stator, and means coupled to said source of electrical energy, said primary winding of said ignition coil and said output winding for energizing said primary Winding of said gnition coil from said source of electrical energy when a voltage above a predetermined magnitude is generated in said output Winding, said rotor and stator including means for generating said voltage above said predeterminedmagnitude in said output Winding for an increasing period in terms of mechanical degrees or rotation of'the engine as the speed of the engine increases. 7

5. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an ignition coil having a primary and a secondary Winding, a distributor driven by the engine for sequentially coupling said secondary winding of said ignition coil to said spark plugs, a source of electrical energy, said distributor including an electrical generator having a rotor driven by the engine, a stator and an outputwinding mounted on said tion of engine speed from low engine speed to a predetermin'ed speed in the middle speed range of the engine and remains substantially constant for engine speeds above said predetermined speed.

6. An ignition system for an internal combustion engine a predetermined magnitude is generated in said output winding, said rotor and stator'including means for generating said voltage above said predetermined magnitude in said output winding for an increasing period in terms of mechanical degrees of rotation of the engine as the speed of the engine increases.

7. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an ignition coil having a primary and a secondary Windin a. distributor driven 'by the engine for sequentially coupling said sec ondary winding of said ignition coil to said spark plugs, a

source of electrical energy, a transistor circuit including a transistor coupling said source of electrical energy to said primary winding of said ignition coil, biasing means coupled to said source of electrical ener y and said transistor circuit for biasing said transistor to. a nonconduct ing state by a biasing voltage of a predetermined magnitude, said distributor including a rotor driven by the engine, a stator and an output Winding mounted on said stator, said output winding coupled to said biasing means, said stator and rotor including means for producing an output voltage in said output winding of a magnitude and polarity to overcome said biasing voltage of a predeter-' mined magnitude for an increasing period in terms of angular degrees of rotation as the speed of the engine increases whereby said transistor energizes said primary Winding of said ignition coil for an increased period in terms of rotation of said distributor'as the speed of the engine increases.

8. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an ignition coil having a primary and secondary winding, a distributor driven by the engine for sequentially coupling said secondary Winding of said ignition coil to said spark plugs, a source of electrical energy, a transistor circuit including a transistor coupling said source of electrical energy to said primary winding of said ignition coil, biasing means coupled to said source of electrical energy and said transistor circuit for biasing said transistor circuit to a nonconducting state by abiasing voltage of a predetermined magnitude, said distributor including a rotor driven by the engine, a stator and an output winding mounted on said stator, said output winding coupled to said biasing means, said stator and rotor including means for producing an output voltage in said output winding of a magnitude and polarity to overcome said biasing voltage of a predetermined magnitude for an increasing period in terms of angular degrees of rotation as the speed of the engine increase in the lower speed ranges of the engine up to a predetermined speed and for tributor as the speed of the engine increases in the lower 1 speed ranges of the engine up to said predetermined speed and energizes said primary winding for a substantially constant period in terms of rotation of said distributor for engine speeds above said predetermined speed.

9. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an electrical energy storage device, means driven in synchronism 1 with the engine for sequentially coupling. said electrical energy storage device to said spark plugs, a source'of electrical energy, an electrical generator driven in'synchronisrn with said first mentioned means, circuit means coupling said electrical energy, storage device, said source of electrical energy and said electrical generator and including means for preventing said source of electrical energy from energizing said electrical energy storage deviceuntil said electrical generatorproduces and maintains a voltage of a i predetermined magnitude, saidelectrical generator including means for generating said voltagev of predetermined magnitude for an increasing period in terms of mechanical degrees of rotation of the engine as the speed ofthe engine increases during thelower speed ranges of the engine.

10. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an ignition coil having a primary and a secondary winding, means drivenin synchronismwith the engine for sequentiallycoupling said L secondary winding of said ignition coil to said spark plugs, V V a source of electrical energy, an electrical generator driven a in synchronism with said first mentioned means,'circuit means coupling said primary winding of said ignition coil, said source of electrical energy and said electrical. generator and including means for preventing said source of electrical energy from energizing said primary winding of said ignition coil until said electrical generator produces and maintainsv a voltage of a predetermined magnitude, 7 said electrical generator including means for generating said'voltage of predetermined magnitude for-an increasing period in terms of mechanical degrees of rotation of. the

' determined speed.

11. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an ignition coil having a primary and a secondary Winding, means driven in synchronism with the engine for sequentially coupling said secondary winding of said ignition coil to said spark plugs, a source of electrical energy, an electrical generator driven in synchronism with said first mentioned means, circuit means coupling said primary Winding of said ignition coil, said source of electrical energy and said electrical generator and including means for preventing said source of electrical energy from energizing said primary Winding of said ignition coil until said electrical generator produces and maintains a voltage of a predetermined magnitude, said electrical generator including means for generating said voltage of a predetermined magnitude for a period in terms of mechanical degrees of rotation of the engine that increases significantly from low or idle speed operation to high speed operation of the engine.

12. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an ignition coil having a primary and a secondary winding, means driven in synchronism with the engine for sequentially coupling said secondary winding of said ignition coil to said spark plugs, a source of electrical energy, an electrical generator driven in synchronism with said first mentioned means, circuit means coupling said primary Winding of said ignition coil, said source of electrical energy and said electrical generator and including means for preventing said source of electrical energy from energizing said primary winding of said ignition coil until said electrical generator produces and maintains a voltage of a predetermined magnitude, said electrical generating means including means for generating said voltage of predetermined magnitude for a substantially constant period in terms of mechanical degrees of rotation of the engine at high engine speeds and for progressively and substantially lesser periods in terms of mechanical degrees of rotation of the engine as the speed of the engine decreases, the period at high engine speeds being at least twice the period at engine idle speeds.

13. An ignition system for an internal combustion engine comprising a plurality of spark plugs, an electrical energy storage device, means operated in synchronism with the engine for sequentially coupling said electrical storage device to said spark plugs, a source of electrical energy and meansdriven by the engine and operated in synchronism with said first means for periodically coupling said source of electrical energy to said electrical energy storage device, said means including means for increasing significantly the period that said source of electrical energy is coupled to said electrical storage device in terms of mechanical degrees of rotation of the engine from engine idle speed up to a predetermined speed and for maintaining said period substantially constant for all speeds above said predetermined speeds.

14. An ignition system for an internal combustion engine comprising a spark plug, an electrical storage device, means operated by the engine for coupling said electrical energy storage device to said spark plug, a source of electrical energy, means driven by the engine and operated in synchronism with the first means for periodically coupling said source of electrical energy to said electrical energy, storage device, said means including means for providing a variable dwell that increases significantly as a function of engine speed from idle speed to a predetermined speed in the middle speed range of the engine for providing a substantially constant dwell for engine speeds above said predetermined speed.

References Cited UNITED STATES PATENTS 8/1948 Short et al. 123l48 6/1960 Kerr l23148 

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE COMPRISING A PLURALITY OF SPARK PLUGS, AN IGNITION COIL HAVING A PRIMARY AND A SECONDARY WINDING, MEANS OPERATED IN SYNCHRONISM WITH THE ENGINE FOR SEQUENTIALLY COUPLING SAID SECONDARY WINDING OF SAID IGNITION COIL TO SAID SPARK PLUGS, A SOURCE OF ELECTRICAL ENERGY, AND MEANS DRIVEN BY SAID ENGINE AND OPERATED IN SYNCHRONISM WITH SAID FIRST MEANS FOR PERIODICALLY COUPLING SAID SOURCE OF ELECTRICAL ENERGY TO SAID PRIMARY WINDING OF SAID IGNITION COIL, SAID MEANS INCLUDING MEANS FOR INCREASING THE PERIOD THAT SAID SOURCE OF ELECTRICAL ENERGY IS COUPLED TO SAID PRIMARY WINDING OF SAID IGNITION COIL IN TERMS OF MECHANICAL DEGREES OF ROTATION OF THE ENGINE AS THE SPEED OF SAID ENGINE INCREASES UP TO A PREDETERMINED SPEED AND FOR MAINTAINING SAID PERIOD SUBSTANTIALLY CONSTANT FOR ALL SPEEDS ABOVE SAID PREDETERMINED SPEED. 